Jaguar IRS in a classic Mustang

[Dazecars]

After much work the third web page documenting my project is done with the exception of needing 2 pictures. This is in my opinion the best of the three pages because it deals with the heart of the issue narrowing the parts and changing the bolt pattern on the wheel flanges. If you are not familiar with my project so far please make sure to look at the first two articles as well. As always please let me know what you think, all comments even ones telling me I have done a poor job so fare are welcome

Mustang IRS Page I
Mustang IRS Page II
Mustang IRS Page III

 

[CochinoFilipino]

Very cool site and projects. Did you take into consideration how/if the shorter half shafts and LCAs will affect performance or your ability to tune the suspension?

 

[Dazecars]

Very cool site and projects. Did you take into consideration how/if the shorter half shafts and LCAs will affect performance or your ability to tune the suspension?

That is a really good point. Lucky for me Jaguar IRS assemblies come in much narrower trackwidths than what I am going to be needing an I was able to crawl under an early XKE an take a bunce of measurements, so I know that I will be just fine.

 

[CochinoFilipino]

Cool. Do any of the stock Jag assememblies come close the Mustangs?

 

[Dazecars]

Cool. Do any of the stock Jag assememblies come close the Mustangs?

The closest units are the ones from 1970-1974 XKE and the 1960 - 1969 3.8s they both measure out at 56" hub to hub as apposed to the 58" hub to hub of a 64.5-66 Mustang

 

[CochinoFilipino]

December issue of HotRod has an article on IRS for Mustangs. All the options are quite pricey. I like your approach.

Did you also narrow the halfshafts by 2.125", the same as the LCA? Or by a proportionate amount? I'm just thinking how/if the camber curve will be affected. I imagine that if both were narrowed 2.125" that he camber gain would be more aggressive?

 

[Dazecars]

I had a similar thought, and was originally going to remove a different amount from the two pieces based on the ratio of half shaft to LCA length observed from the original XJ6 pieces. However after getting the opportunity to crawl under an early XKE with the narrower track width I soon realized that basically the same amount had been added to both pieces when Jaguar increased the length of unit for the XJ6.

 

[CochinoFilipino]

Is there any toe adjustment in the jag unit? If so, is it a static adjustment?

 

[Dazecars]

I have not looked that much in to alignment. I know how to adjust camber, and caster is fixed based on how the unit is mounted. I am not sure if there are any toe adjustments. I am thinking that there is not because the wheels are relatively fixed and with the wishbones and trailing arms fixed the wheels should not move toe in or out during driving.

These seem like questions from some one who is seriously contemplating the rear end in their car???

 

[CochinoFilipino]

These seem like questions from some one who is seriously contemplating the rear end in their car???

Your post coming up at the same time as the hotrod article has me day dreaming about it. And the diferent designs have piqued my curiosity enough to look into them. Right now I just want get her back on the road and drive her. But IRS is a real possibly in the long run

 

[bnickel]

something to consider is that the Jag IRS does not have an UCA, some say it's nod needed for just a cruiser but if you plan on doing some serious corner carving you should consider something with an UCA. one of these days i plan on building a clone of the IRS in the 68 shelby prototype coupe, the EXP500 or "green hornet" as most people call it. barring that, i'd seriously consider one of the DVS restorations kits for the cobra IRS.

 

[65mistress]

With that said, what's the strength difference between the Jag and Cobra units? I don't plan on making a 600 hp ground pounder, I'd love to, but it's just not feasible at this point. If after putting the Jag unit in, I wanted to put in a Twin Turbo 351 in, would I be changing out the rear unit back to a beefy 9" or with either the Jag rear or the Cobra rear be enough?

I really liked your articles written so far.

 

[Dazecars]

something to consider is that the Jag IRS does not have an UCA, some say it's nod needed for just a cruiser but if you plan on doing some serious corner carving you should consider something with an UCA. one of these days i plan on building a clone of the IRS in the 68 shelby prototype coupe, the EXP500 or "green hornet" as most people call it. barring that, i'd seriously consider one of the DVS restorations kits for the cobra IRS.

I understand what you are saying, and really appreciate your comments and concerns however I simply do not see it as an issue. The weakest link is the half-shaft u-joints and the ones used are quite a bit bigger than the standard Mustang driveline u-joints. The average Jaguar weighs in the 4000# range, well over 1000#s more than the average Mustang. As long as the u-joints are routinely checked as recommended every 10K miles than I simply do not see the half shaft as an UCA being an issue. Lets look at the reel world track record, this system was used for over 30 years on both the street and track, behind some V12 Motors as well as those that swapped out the Jag motors for performance Chevy 350s, if the half shaft being the UCA was that big of an issue I think Jaguar would have changed their design IMHO

I do agree that the Cobra IRS is a strong well built system however it is expensive, and will not fit under a 64.5-66 Mustang with out modifying the fenders which in my mind makes it a non option for these cars.

 

[Dazecars]

A stock Jaguar differential is rated at 500 HP. There are improved components that can be installed to take it far beyond this mark. I even know a guy who has a Jaguar IRS in his mustang and races it. Did I mention his car pouts out 600 RWHP I think the Jag rear end is up to the task

 

[CochinoFilipino]

,,,,, one of these days i plan on building a clone of the IRS in the 68 shelby prototype coupe, the EXP500 or "green hornet" as most people call it. barring that, i'd seriously consider one of the DVS restorations kits for the cobra IRS.

If I were to roll my own, I'd borrow some design ideas from team321 . They connected the toe adjustment 'arm' to the LCA. But if it was mounted to the cradle seperately and placed properly you could tune in some rear stearing.

 

[bnickel]

notice they added an upper control arm. i wasn't commenting on the strength of the jag IRS but more geometry, the camber curve on them isn't very good. the c3 vette had a similar design and vintage racers know that with an UCA they'd be able to turn much facter lap times but they are limited by the rules and aren't allowed to add them.

 

[SLVRBOY]

that is a great job you did with the articles. ive been looking at putting an irs in my 67 but couldnt find anything reasonably priced, i have already contacted the guy you got your jag irs from. that should let me put the 18x10 wheels i want on the back. keep up the good work .

 

[Dazecars]

that is a great job you did with the articles. ive been looking at putting an irs in my 67 but couldnt find anything reasonably priced, i have already contacted the guy you got your jag irs from. that should let me put the 18x10 wheels i want on the back. keep up the good work .

Glad you liked my information. I am working on the text for page IV now and hope to get it done by the first of the year. When dealing with David make sure to let him know where you found out about the Jaguar IRS units and he should give you a little bit of a discount.